In a panel instrument and the like in which modular components can be customized and added, in many cases, a circuit board is fixed to a resin holder in a snap-fit manner and the resin holder is coupled to a housing in a snap-fit manner. The snap-fit is one of the coupling techniques of two components and is commonly used.
On the other hand, in a case where the circuit board is to be detachably mounted, coupling in a snap-fit manner is not suitable. That is, in a case where the snap-fit is used as a mounting and demounting method, there is a concern that an excessive load is applied to a snap-fit portion and thereby destruction and fatigue failure of the snap-fit portion can occur, and a coupling function is lost.
With respect to this, conventionally, a lock structure is known which locks mounting and demounting of a plurality of circuit boards stored in a row within a housing (for example, see PTL 1). In the lock structure disclosed in PTL 1, a block-shaped lock member having grooves corresponding to storage clearances of the circuit boards is mounted on the housing to be slidable in an arrangement direction of the circuit boards. Then, in a state in which the lock member is slid in one direction and the grooves of the lock member are aligned with storage positions of the circuit boards (unlocked state), mounting and demounting of the circuit boards can be performed. In addition, in a state in which the lock member is slid in the other direction and the grooves of the lock member are shifted from the storage positions of the circuit boards (locked state), the circuit boards abut against the lock member and thereby mounting and demounting of the circuit boards is limited.